1. Field of the Invention
The present invention relates, in general, to the desulfurization of flue gas in closed vessels where liquid is sprayed into a gas stream and in particular, to a new and useful arrangement and method for measuring liquid flow in a vessel using the flow pressure at the liquid spraying nozzle.
2. Description of the Related Art
It is well-known that the accurate determination of liquid flow in a flue gas desulfurization (FGD) system is essential to evaluate and optimize the performance of the entire system. Conventional methods such as measuring pump drawn currents and pump total developed head depend largely on the condition of the pump and a well-developed knowledge of the system's resistance. These methods attempt to measure the flow by following measuring the performance of the source and assume that the rest of the system is operating as designed. Ultrasonic meters have been used for such measurements and are nonintrusive; however, they require a certain length of pipe which may not be available in a lot of instances. Magnetic meters have also been used, but are intrusive and require a straight pipe which may not be readily available. Additionally, orifices also have been used; however, the erosive nature of the slurry make their use limited. Moreover, orifice meters are not suited for flow measurements in a vertical run of pipe because of slurry deposition on the downstream face of the orifice and the continuous change in its flow characteristics. In horizontal pipe runs, eccentric orifices are used to reduce both upstream and downstream slurry deposition, but they are susceptible to erosion.
Some global problems encountered with orifice meter use include: the restriction of flow into the header; therefore, unless the system is designed with the orifice meter in mind, the flow characteristics of the system are expected to change with the introduction of the orifice; the flow measured by the orifice is an indication of the flow at the orifice location and if multiple headers branch downstream of the header, there is no indication of the flow at the delivery point to the nozzle; the characteristics of the orifice changes as erosion takes its toll on the orifice; and slurry from the FGD system gets into the orifice taps thereby plugging them, and rendering the orifice useless after a short period of time.
Additionally, pressure gauges having diaphragms have been used in measuring procedures and tend to protect the gauge and overcome the plugging problem. However, they do not solve the other problems encountered with orifices such as those listed above.
Presently, there is no known system or method for measuring fluid flow in a FGD system which is accurate, efficient and has the ability to make direct measurements at the liquid spray nozzle.